Zinc Production Plant Research Articles

RARE-EARTH elements in the topsoils of a Russian industrial city: Sources and human health risk assessment

Research on rare-earth elements (REEs) in urban soils of Russian industrial cities is extremely limited. This study investigates the potential sources and human health risks of REEs contained in the topsoils of the industrial Russian city of Chelyabinsk. The study also takes into account natural sources of REE as the city is located on the border of granites (Urals) and sedimentary rocks (Western Siberia). We analyzed the concentration and distribution of REEs in the soils of four types of locations: residential courtyards, city parks, roadsides, and industrial locations. The total REE concentrations ranged from 44 to 255 mg/kg, with average concentrations of 140, 124, 113 and 89 mg/kg in the courtyards, roadsides, industrial location and city parks, respectively. The REE content in courtyard soils could be influenced by poor cleaning of fallen leaves. The ratios of light REE (LREE) to heavy REE (HREE) ranged from 9.5 to 10.1, revealing an obvious fractionation between them. The fractionation of LREE and HREE, and the REE/ES (European Shale) pattern showed that REE accumulation in Chelyabinsk soils has been disturbed by human activities. It was shown that the dust from industrial emissions was the main anthropogenic source of REE accumulation in urban soil. The largest amounts of REEs are emitted from an electrometallurgical plant and zinc production plant. Fortunately, the estimated daily intakes of REE from soils for children and adults were well below the safety thresholds. At the same time, in order to prevent social tension and reduce the anthropogenic load on the urban area, it is recommended to use phytoremediation technologies, smart landscaping of industrial and residential areas, more thorough cleaning of fallen leaves and road dust. It is also recommended to move the most dangerous production processes outside the urban area.

Recovery of lead from the leaching residue derived from zinc production plant: process optimization and kinetic modeling

ABSTRACT This study aimed to extract lead from a zinc production plant residue containing 3.67% PbO, 2.79% ZnO, 8.75% SiO2, 24.8% SO2, 2.38% Fe2O3, and 4.46% Al2O3. In this regard, response surface modeling based on the central composite design was utilized to scrutinize and optimize the operating parameters such as NaCl concentration, HCl concentration, pulp mixing rate, solid percentage, and leaching time on the leaching efficiency of lead. Our findings demonstrated that NaCl concentration and solid percentage were the most effective parameters on the leaching of lead, in which higher concentrations of chloride and lower solid contents led to an enhancement in lead recovery. To attain the maximum recovery of lead (75.72%) at room temperature, the optimum conditions were found to be 2 mol/L HCl, 350 g/L NaCl, solid percent 10%, stirring rate 300 rpm, and leaching time 90 min. The leaching kinetics was also examined based on the shrinking core models to realize the process mechanism and develop a new kinetic model. The results exhibited that the kinetics control mechanism was the product layer diffusion model with an activation energy of 16.69 kJ/mol. Finally, a kinetic model is developed based on the diffusion model and effective parameters.

A review of processing methods for electric arc furnace dust

The work presents an analytical review of processing methods for industrial waste from the ferrous industry, namely, electric arc furnace dust. The annual emissions of this dust and the source of each dust component are determined. Scientific works on the topic of processing electric arc furnace dust published over the past 20 years are compared and analysed. The major methods for dust processing to recover iron, zinc and other metals include pyro - and hydrometallurgical techniques and their combinations. To date, several high-temperature technologies have been developed that allow zinc-containing dust to be efficiently processed (in particular, the Waelz process and secondary processes). However, many of these technologies have remained at the development stage for various reasons (either requiring considerable capital investments, or being unreliable, energy-intensive and inefficient). It is shown that hydrometallurgical processes are environmentally safe and selective to valuable components and allow technological parameters to be controlled. By selecting a suitable solvent (acidic or alkaline), the required metal can be selectively extracted from dust. In addition, such a technology will be cost-effective even under low contents of the extracted component. Approaches to processing metallurgical dust with inorganic and organic acids and ammonia-based solutions are described. Both conventional processing of electric arc furnace dust on an industrial scale and the laboratory developments recently introduced at zinc production plants (their features, advantages and disadvantages) are discussed. Technologies that allow valuable components in the dust to be extracted and returned to the production cycle are identified.

Providing Practical Instruction for Solving Environmental Problems from Residue (cake) of Cold Purification Process in Zinc Production Process

Background and Objective: In the waste from the cold treatment process in zinc production plants, there is about 40 to 50% of zinc and other harmful heavy metals such as cadmium and nickel. Cadmium and nickel are among the heavy metals that are harmful to human health in high concentrations. Removal of bio-pollutants from these wastes is one of the concerns of the zinc industry. The purpose of this study is to remove nickel and cadmium as impurities in the zinc production process by cementation method. Methodology:The procedure consists of three steps: cold purification cake leaching, impurity purification and electrolysis. The cake is first liquefied with sulfuric acid and the resulting solution contains zinc ions along with nickel and cadmium impurities. Optimal conditions for the removal of impurities were obtained by the surface response method (RSM), then the filtration process was performed by the cementation method and the impurities were removed and finally the solution was electrolyzed to produce zinc. Using Design Expert (DOE) test design software, the parameters affecting the filtration process such as temperature, zinc powder concentration, retention time and additive concentration were investigated. Findings: It was found that most influences related to contact time, temperature, zinc powder amount and additive concentration, respectively. So, optimum conditions for removal of nickel and cadmium containing temperature of 85 centigrade, concentration of 6.63 mg L-1 of zinc powder, contact time of 100 min and concentration of 10.29 mg L-1 for additive were obtained. At these conditions, impurities amounts were reached to the allowed limit for electrolysis and zinc in the cake was recovery. Conclusions: Using cementation method by removing impurities and then recovering zinc, in addition to solving some of the environmental problems caused by the cake, the recovery of these metals is of great economic importance.

Thermo-environmental evaluation of a modified Waelz process for hazardous waste treatment

Electric arc furnace dust is a waste by-product of electric arc furnaces in steel production. This material is hazardous to the environment due to the presence of metals, such as chromium, lead, and cadmium; in addition to these, there is zinc in its composition. One of the main ways of recovering zinc from the electric arc furnace dust is carried out in rotary kilns called Waelz kilns. This work aims to develop a model of a Waelz kiln and evaluate the impact of processing sludge from an industrial effluent treatment plant as a feed along with electric arc furnace dust, with and without the inclusion of a drying system for the sludge and a thermal integration system with the Waelz slag. The model, validated against industrial data plant, revealed an optimum operational point, resulting in a zinc recovery of 98.3 %, which is equivalent to an increase in the production by 6.2 %. The scenario with direct sludge feed into the kiln resulted in a maximum zinc recovery rate of 89 %. The results from the sludge drying scenario imply a zinc recovery of 94 % and represent a viable alternative for reducing the amount of solid waste generated in the zinc production plants that use the Waelz kiln by 1100 t/year per tonne of sludge treated. Furthermore, it also increased zinc production to 1300 t/year.

Selective Emulsion Liquid Membrane Extraction of Cu(II) Mediated by a Schiff Base Ligand

This study concerns on the application of a Schiff base ligand of type N3O2 as a carrier in a water-in-oil emulsion liquid membrane for the selective transport of copper ions. A hydrochloric acid solution formed the internal aqueous phase (receiving phase), and the membrane was composed of a Schiff base ligand called bis(1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine (L) in dichloromethane and the non-ionic surfactant Span® 80 in paraffin. By applying the optimum conditions, a quantitative uptake of copper ions (initial concentration 5 mg L-1) from the aqueous feed phase (pH 5) into the receiving phase (hydrochloric acid 0.7 mol L-1), after 10 min was attained. The optimal value determined for the treat ratio allows achieving to a concentration factor of >6 for the copper ions in the receiving phase. The proposed emulsion liquid membrane provided an excellent selectivity towards copper ions with respect to some associated metal ions including Cd(II), Ni(II), Zn(II), Co(II), Fe(II), and Cr(III). However, such selectivity was not observed in the competition of Cd(II) and Pb(II) ions. The breakage of emulsions and recovery of the internal phase from the membrane was performed by freezing the internal solution. In fact, the expansion of the frozen internal phase volume results in breakage of the emulsions. The applicability of the proposed procedure was appraised by employing the method for the recovery of copper from the leached solutions of the cobalt and nickel-cadmium filter-cakes of a zinc production plant.

Extremely high concentrations of zinc in birch tree leaves collected in Chelyabinsk, Russia.

Zinc is an essential trace element and a vital microelement for human health. Zinc can be toxic when exposures exceed physiological needs. Toxic effects in humans are most evident from inhalation exposure to high concentrations of Zn compounds. Urban air pollution can be especially dangerous due to the Zn content in airborne dust. Tree leaves can absorb significant levels of zinc. In this study, leaf deposition of Zn was investigated in Chelyabinsk, Russia. Russian zinc production plant and metallurgical plant are located in Chelyabinsk. Extremely high concentrations of Zn (316-4000mgkg-1) were found in the leaves of birch trees. It is well known that traffic also is Zn source in an urban environment. Trees, growing at the different distances from zinc productionand metallurgical plants and road to identify the contribution of each source (road or industry), were studied. Through SEM analysis, the prevalence of small particulates (PM10 and less), containing Zn, illustrated leaf Zn deposition from the air by passing root accumulation. It was shown that emission of zincproduction plant and the metallurgical plant is the main source of leaf Zn deposition in Chelyabinsk.

Short Communication: Effect of urban greening and land use on air pollution in Chelyabinsk, Russia

Abstract. Krupnova TG, Rakova OV, Plaksina AL, Gavrilkina SV, Baranov EO, Abramyan AD. 2020. Effect of urban greening and land use on air pollution in Chelyabinsk, Russia. Biodiversitas 21: 2716-2720. Chelyabinsk is a major industrial Russian city that faces diverse environmental issues, the most important of which is air emissions. The primary sources of air pollution in Chelyabinsk are industry (concrete product plants, ferrous and nonferrous metallurgy such as zinc production plants, and pulp production), thermal power stations, and transport. People have known that trees can help to reduce air pollutants for a long time. We studied 8 zones within a radius of one kilometer from state air pollution monitoring stations. Eight land-use types such as industrial category, residential category, natural and semi-natural broadleaved vegetation, natural and semi-natural coniferous vegetation, broadleaved forest, coniferous forest, artificial broadleaved vegetation, and artificial coniferous vegetation, were obtained. The response of air pollution to land-use and urban greening was analyzed. Analysis results showed that there was no correlation between industrial and residential categories of land-using and concentrations of the most dangerous air pollutants in Chelyabinsk (formaldehyde, hydrogen fluoride, and nitrogen dioxide). The dominant factor affecting urban air quality was urban greening.

Hybrid fuzzy control for the goethite process in zinc production plant combining type-1 and type-2 fuzzy logics

The goethite process is a complicated reaction system which holds a significant position in zinc hydrometallurgy process. It exhibits nonlinear behavior and time-delay nature because of the chemical reactions. To achieve the stable and real-time control performance, a hybrid fuzzy control strategy integrating a type-1 and a type-2 fuzzy logic controllers is proposed in this paper. According to the on-line measured pH, the type-1 fuzzy controller (T1 FLC) via the Takagi–Sugeno fuzzy control is employed to control the zinc oxide additive rate. A parameter tuning method that does not require the system model is designed for the T1 FLC. Because the ferrous ion concentration cannot be measured on-line, the interval type-2 fuzzy logic controller (IT2 FLC) is utilized to control the oxygen flow rate. According to the feedback information, gradient descent algorithm is used to update the parameters in the IT2 FLC. Because of the unknown system structure, gradient descent information is estimated by the simultaneous perturbation stochastic approximation. Finally, simulations are conducted using the practical production data. The simulation results show the effectiveness of the proposed strategy. The hybrid fuzzy control strategy improves the control performance of the goethite process, compared with PID controller.

Emission of Unintentionally Produced Persistent Organic Pollutants from Some Industrial Processes in Northern Vietnam.

Concentrations of PCDD/Fs, dioxin-like PCBs (dl-PCBs), PeCB and HCB were determined in flue gas, fly ash and bottom ash samples collected from brick production, steel production, and zinc production plants, an industrial waste incinerator and a medical waste incinerator in northern Vietnam to understand the contamination levels, accumulation patterns and extent of emission. Total TEQs concentrations of PCDD/Fs and dl-PCBs in flue gas and ash samples from these industrial plants ranged from 0.304 to 50.55pg/Nm3 and 1.43 to 440pg/g, respectively. PeCB and HCB residues in flue gas samples ranged from 0.839 to 46.59ng/Nm3 and 1.16 to 60.5ng/Nm3, respectively. The emission factors of 4.8-740 ngTEQs/tonne for PCDD/Fs and dl-PCBs, 67.12-240.7µg/ton for PeCB and 11.64-889.3µg/ton for HCB were obtained in flue gas samples. This is among the first reports on the emission factor of PCDD/Fs, dl-PCBs, PeCB, HCB in brick production, zinc production and waste incineration in Vietnam.

Levels, profiles, and emission characteristics of chlorobenzenes in ash samples from some industrial thermal facilities in northern Vietnam.

Chlorobenzenes (CBzs) are unintentionally produced organic contaminants from different thermal industrial processes, which have been scarcely surveyed in Asian developing countries including Vietnam. In this study, residue concentrations, profiles, emission factors, and annual emissions of seven chlorobenzene compounds were investigated in fly ash and bottom ash samples of some industrial facilities including brick making plant, steel and zinc production plants, and industrial and municipal waste incinerators in northern Vietnam. Total concentrations of seven CBzs in the ash samples were generally decreased in the order: industrial waste incinerator > municipal waste incinerator > steel-making plant > brick making plant. Emission pattern of CBzs varied considerably among different industrial plants, with 1,2- and 1,3-dichloro-, 1,2,3,4-tetrachloro-, and hexachlorobenzene as predominant compounds in the industrial waste incinerators and steel-making plants. Emission factors of CBzs estimated for the fly ash and bottom ash samples were in the range of 118-2020 and 5.3-22,600μg ton-1, respectively. Average annual emissions (AEs) of total seven CBzs estimated for fly ash and bottom ash in the investigated plants were in the range of 154-54,300 and 20,160-161,400mgyear-1, respectively. The AEs of CBzs estimated for fly ash in the steel-making plant were higher than those in the waste incinerators. Meanwhile, CBz emissions for bottom ash were the highest in the steel-making plant, followed by the industrial and municipal waste incinerators. This is among the first studies on the emission characteristics of both low and highly chlorinated benzenes from industrial activities in Vietnam.

An attempt of optimization of zinc production line

The goal of the research is an attempt of optimization of the hydrometallurgy-based zinc production line, consisting of three stages: mixing of raw materials, oxidative roasting and leaching. The output product of one stage is an input to the next stage. Goal of mixing is preparation of zinc concentrates mix on the basis of zinc concentrates originated from different mines. The output semi-product of the next stage, the oxidative roasting process, is calcine, which is the input of the leaching. The result of the leaching is zinc sulfate solution and the goal of leaching is to carry out the maximum amount of zinc to solution. The preliminary step of any optimization is modeling of the analyzed processes. Modeling of considered three stages of zinc production line, based on the real industrial data of one of zinc production plants, was performed using different techniques. The elaborated models were the basis of the optimization for given objective functions of each of the production stages. The optimization methodology of multi-stage processes developed by the authors was applied. Obtained results of modeling and optimization are presented.

Assessment of spatial distribution pattern of heavy metals surrounding a lead and zinc production plant in Zanjan Province, Iran

The present study aimed at characterizing the spatial distributions and investigating the contents of six heavy metals (Co, Ni, Cu, Zn, Cd and Pb) in top soils, surrounding the National Iranian Lead and Zinc Company (NILZ) in Bonab Industrial Estate (Zanjan-Iran) by Geostatistical analyst and Moran's I autocorrelation index. The soil samples (126) were collected from the area with a radius of 5km of the NILZ Company. The average amount of Co, Ni, Cu, Zn, Cd and Pb metals were 4.16mgkg−1, 26.38mgkg−1, 18.31mgkg−1, 684.11mgkg−1, 5.79mgkg−1, and 119.59mgkg−1, respectively. Principal Components Analysis (PCA) classified the investigated heavy metals in two groups. These groups were Factor I (Pb and Cu) and Factor II (Co, Ni, Zn and Cd) that confirm exist the anthropogenic source of the pollutants. Moran's I autocorrelation index was cleared that the high–high spatial clusters of topsoils contaminated with heavy metal were located in the center of study area, near NILZ Company. It was deduced that the company activities have a big impact on distribution of heavy metal in study area. Geostatistical analysis revealed that the high values of all studied heavy metals were located near the NILZ Company. According to comparison the prepared and land use maps, it was cleared that pesticides and chemical fertilizers, geochemistry and anthropogenic sources are the main factors in spatial variation of heavy metals.

Mass transfer correlation of simultaneous removal by cementation of nickel and cobalt from sulfate industrial solution containing copper

Abstract In this part I of our work, the kinetics study of simultaneous cementation of nickel and cobalt from industrial zinc sulfate solutions using a rotating zinc electrode disc was investigated. Experiments were carried out in the presence of copper to increase the low cementation rate of these elements (Ni and Co). The effect of temperature, metallic ions concentrations and electrode rotation speed was also investigated. The reaction of nickel cementation was found to be under diffusional control while that of cobalt was found under chemical control. The reaction rate was found to be strongly affected by the increase in the electrode surface area. Mass transfer study of the process was correlated by the equation: Sh = 1.43 Sc 0.33 Re 0.49 . The results obtained will be used to establish optimal conditions for the zinc production plant of ALZINC, Tlemcen, Algeria.

Exposure to sulfuric acid in zinc production.

This study characterized workers' exposure to sulfuric acid in two cell houses of a zinc production plant. We also aimed at estimating previous exposure to sulfuric acid by simulating the process conditions from before 1975 to produce exposure data for an epidemiological study on cancer in this industry. Further, we compared different sampling methods for aerosols in the cell houses. Personal sampling with a 37 mm Millipore cassette showed that the geometric means of the exposure levels for the workers in the two cell houses were 0.07 mg/m3 (range 0.01-0.48 mg/m3) and 0.04 mg/m3 (range 0.01-0.15 mg/m3). Norway's newly revised limit value of 0.1 mg/m3 was exceeded in 39.0 and 12.9% of the samples in the two cell houses. After the foam layer was removed from the electrolyte surface to simulate the production process from before 1975, the concentration of sulfuric acid increased from 0.11 to 6.04 mg/m3 in stationary measurement by the Millipore sampler. Stationary sampling showed that the Millipore sampler and the inhalable fraction of the Respicon impactor underestimated the sulfuric acid concentration by factors of 1.5 and 2.1 compared with the Institute of Occupational Medicine (IOM) sampler. Sampling with the Respicon impactor showed that the respirable, tracheobronchial and extrathoracic fractions constituted 3.0, 18.7 and 71.7% of the inhalable sulfuric acid aerosol, respectively. Today's exposure levels are lower than those reported to be associated with an increased prevalence of laryngeal cancer in other industries, but the levels prior to 1975 seem to have been much higher. By mass, most of the inhalable aerosol was in the size fractions considered to be highly relevant for the effects of sulfuric acid on the respiratory system. The risk of cancer among the cell house workers should be investigated in an epidemiological study.

Removal of cobalt and nickel from zinc sulphate solutions using activated cementation

The influence of different parameters (duration, temperature, zinc dust quantity, concentration of activators - copper and antimony) on the process of activated cementation of Co and Ni has been studied. We have worked with industrial zinc sulphate solutions. During the process of activated cementation of Co and Ni, copper (involved as CuSO4.5H2O) and antimony (involved as Sb2O3) were used as activators. The lowest values of Co content have been obtained at a temperature of 80-85 oC, CCu = 200-300 mg/dm3 and 18 multiple surplus of zinc dust. After adding Cu to the solution, mainly the cementation of Ni is activated, and that of Co is activated to a lower degree. It was found that when GSb : GCo ratio is between 0.5 : 1 and 2 : 1, the solution is purified from Co and Ni to a great degree. After intensive stirring and increasing the duration of the process the cement sediments dissolve reversely. This holds true of Co to a greater extent, as compared to Ni. The results obtained will be used to establish optimal conditions for the carrying out of activated cementation in Zinc Production Plant in KCM SA, Plovdiv.

Purification of zinc sulfate solutions from cobalt and nickel through activated cementation

The influence of reaction time, temperature, zinc dust quantity and concentration of copper and antimony activators has been studied on the process of activated cementation of Co and Ni from industrial zinc sulfate solutions. Copper sulfate and potassium antimony tartrate were used as activators. The results obtained will be used to establish optimal conditions for activated cementation of cobalt and nickel in the Zinc Production Plant in KCM, Plovdiv.

Synthesis gas production by zinc oxide reaction with methane: elimination of greenhouse gas emission from a metallurgical plant

Most natural gas based petrochemical processes consist of catalytic reforming or partial oxidation units for producing synthesis gas. This research shows that it is possible to replace these units by the reaction of zinc oxide with methane, which produces metallic zinc and synthesis gas (CO + 2H 2) simultaneously. Therefore, by combination of the metallurgical and petrochemical units, it is possible to eliminate the greenhouse gas emission from a conventional zinc production plant. On the other hand, synthesis gas from the ZnO + CH 4 reaction can be used for making petrochemical products. In this work, the reaction of zinc oxide with methane was studied by thermogravimetry and online gas analysis with a mass spectrometer. The main goal of this article is the study on the nature of gaseous products and H 2/CO ratio of produced synthesis gas. Therefore, a basic method for quantitative gas analysis by mass spectrometer was introduced, and its accuracy was checked with the decomposition products of a standard material. Mass spectrometer results of the ZnO + CH 4 reaction showed that synthesis gas with a H 2/CO ratio of about two is produced, which is very suitable for methanol production plants. Finally, the necessary kinetic parameters of this reaction for design of industrial plants were presented.

Treatment and recycling of zinc hydrometallurgical wastes by self-propagating reactions

A novel technique for treating and recycling of a highly toxic solid waste from electrolytic zinc plants, i.e. goethite waste, is proposed. It consists of blending this waste with suitable amount of reducing agents (aluminum or aluminum and silicon) and ferric oxide, and igniting the resulting mixture so that a self-propagating reaction in the form of a combustion wave rapidly travels through the mixture without requiring additional energy. Reactants are converted into two solid products (P 1 and P 2) with different mass, composition and structure, and a gas constituted by SO 2. Aluminum and silicon should be preferred as reducing agents, since the reaction product P 1 obtained in larger quantity, is constituted by an amorphous glassy structure of alumino-silicates which embodies heavy metals, such as Pb and Cd. Leaching tests of the reaction products P 1 are also performed to verify the possibility of their disposal. The solid product P 2 on the other hand may be recycled in the roasting unit of the industrial zinc production plant. A waste treatment process is also proposed.

The Removal of Cr(VI) from Aqueous Solutions using Zinc Extraction Residue

This study deals with the removal of Cr(VI) from aqueous solutions by using filter cake known as zinc extraction residue (ZER) generated as a by product in a zinc production plant located in Kayseri-TURKEY. It was found that ZER, which is rich in lead compounds, has a great affinity for chromate ions. The Cr(VI) removal yield decreased with increasing initial concentration of Cr(VI) solution. An increase in the dosage of ZER caused an increase in the removal yield and the concentration of Pb, Cd and Zn released from ZER into the treated solution. The effect of temperature showed the removal process is endothermic. The removal process was highly pH dependent. 100 % removal of Cr(VI) was obtained at initial pH about 5.0 and 11.0 for the initial Cr(VI) concentration of 100 mg l−1 at 25 °C and 5 mg l−1 ZER dosage for contact time of 60 min. The removal percentage of Cr(VI) declined at pHs other than those mentioned above. Minimum removal (26.5 %) was observed at initial pH value of 3.05. XRD analysis showed that low-solubility lead chromates were formed in the removal process.